BEIRUT — Syrians disagreed Tuesday about what a new Russia-Turkey deal means, casting into doubt whether it will ultimately prevent a potentially devastating war for control of the Syrian province of Idlib.

The deal announced Monday has been broadly welcomed as an opportunity to forestall the full-scale Syrian government offensive against Idlib that has been widely feared, averting the humanitarian catastrophe it was expected to trigger.

Under the broad terms of the agreement outlined by Russian President Vladimir Putin and his Turkish counterpart, Recep Tayyip Erdogan, Russia and Turkey will jointly oversee the creation of a nine-mile demilitarized zone between rebel and Syrian government lines intended to keep the two sides apart.

But it remains unclear whether the deal will prevent an eventual conflict in the area, said Lina Khatib of London’s Chatham House think tank.

“We definitely should not think that the Idlib deal is the ultimate deal. What we are seeing is only a measure for the time being. It is not the endgame for Idlib,” she said. “At best, this deal postpones a potential confrontation in Idlib rather than completely eliminates the possibility of an offensive.”

Unusually for Syria, however, the deal was welcomed by all sides as an opportunity to avert, at least for now, the immense suffering that a battle would inflict on the more than 3 million civilians in the northwestern province. It would also avoid the heavy losses that government forces would incur in launching the biggest battle of the Syrian war.

The Syrian government said in a statement carried by the official Syrian Arab New Agency that it “welcomed any initiative that stops bloodshed and contributes to security and stability in each inch that was struck by terrorism.”

Iranian Foreign Minister Mohammad Javad Zarif said Iran, a close ally of Syria, played a role in negotiating the agreement, which he hailed as evidence that “diplomacy works.”

Idlib residents took to the streets to demonstrate against Syrian President Bashar al-Assad and celebrate their relief that an offensive had at least been deferred.

This file photo posted on the Twitter page of Syria's al-Qaeda-linked Jabhat al-Nusra on April 25, 2015, shows the group’s fighters in the town of Jisr al-Shughour, in Syria’s Idlib province. (Nusra Twitter page via AP)

But it also appeared as though the government and the Syrian opposition have different understandings of where the deal will lead, calling into question its chances for success. All that is known for now, according to the statements issued by Putin and Erdogan, is that the demilitarized zone is to be established by Oct. 15 along a horseshoe-shaped line roughly corresponding to the borders of Idlib province.

Extremist-linked groups are expected to retreat from the buffer zone to areas farther north. The Turkish-backed rebels in the area are allowed to remain but are expected to move their heavy weapons out of the zone.

No further details were given, leaving many questions unanswered, including the eventual fate of the province.

According to Russian diplomats quoted by the pro-regime Syrian daily al-Watan, the plan envisages a second deadline in November by which all rebel and extremist groups are to surrender their heavy weapons throughout Idlib province. The Syrian government would then restore its authority across the province by the end of the year, al-Watan said.

Capt. Naji Mustafa, a Syrian rebel spokesman, said the opposition has not been informed of any such arrangements and would not agree to the return of Assad regime authority in any part of Idlib. Although the rebels welcome the halt to plans for an imminent offensive, they are going to refrain from committing to the deal, including the surrender of heavy weapons, until the details have been made available, he said.

“Until now, we only have the highlights,” he said. “We need details.”

One concern, Mustafa said, is that the rebels would surrender their artillery, tanks and armored vehicles only to be subjected to a government offensive after all.

“The Russians are known to be deceitful and untrustworthy, and we are going to keep up our vigilance against being double-crossed,” he said. “They have not abided by agreements in the past, and we don’t trust the Russians.”

It is also unclear whether the al-Qaeda-linked groups in the area would agree to leave, given the understanding repeatedly stated by Russia and Turkey that the goal is to eliminate extremist groups from Idlib, said Sam Heller of the International Crisis Group. Those groups include Hayat Tahrir al-Sham, which was formerly known as Syria’s al-Qaeda affiliate Jabhat al-Nusra, and Hurras al-Deen, a smaller al-Qaeda-allied group.

It will presumably fall to Turkey to persuade the Islamist militant groups to leave, but how is not spelled out, Heller said. “What has been disclosed publicly as part of this new deal seems as if it would be intolerable to Tahrir al-Sham,” he said.

Russia and Turkey may not have figured out all the fine print yet, Khatib said, and the agreement at least buys time for them to continue negotiations and secure buy-in from their respective allies.

Working to the deal’s advantage are the geopolitical alignments that favor a continued alliance between Turkey and Russia in Syria, she said. Russia has an interest in keeping Turkey on the side to secure Moscow’s broader ambition of establishing itself as an important regional player beyond Syria’s borders.

Turkey has a stake in upholding its Russia alliance as a lever against U.S. support for the Kurdish militia in northeastern Syria, which Erdogan described as the “biggest threat” to Syria’s future.

“The deal will succeed if both sides are committed, and they seem to be,” said Mohammed Karkas, a Syrian opposition supporter in the Idlib town of Maarat al-Numaan. “I think this deal will work because it’s a deal between nations, between governments.”

Zakaria Zakaria in Istanbul and Susan Haidamous in Beirut contributed to this report.